The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems are typically used to etch thin film on substrates such as semiconductor wafers. Etching usually includes either wet chemical etching or dry etching. Dry etching may be performed using plasma generated by inductively-coupled plasma (ICP). The inductively-coupled plasma may be generated by coils arranged outside of a processing chamber adjacent to a dielectric window. Process gas flowing inside the processing chamber is ignited to create plasma. In some applications, RF plasma power is output to one or more inductive coils that are arranged outside of the processing chamber. RF bias power may also be supplied to an electrode in the substrate support.
The frequency of the RF plasma power or RF bias power can be varied to provide additional process control. In addition, a magnitude or level of the RF plasma power or the RF bias power can be varied during processing to provide additional process control. Changes in the RF plasma power or level and/or the RF bias power or level can cause changes in the impedance seen by the drive circuit. When an impedance mismatch occurs between the load and the drive circuit, power is reflected, which is inefficient.